The Anti-gravitational Heat Transfer Performance Of The Multi-evaporator Capillary Pumped Loop And Numerical Simulation Of Heat Enhancement Using Ferrofluid

With the rapid development of the microelectronic manufacturetechnology, such as the microprocessors, the increased density ofpackaging, the density of integration and the capability of microelectronicsare in continual improvement. As a result, more heat flux is generatedwhile these microprocessors working. This brings higher requirements tothe heat dissipation of the microprocessors. Heat pipes are usedextensively for heat dissipation and energy saving because of their highefficient heat transfer performance, the absence of moving parts, as well astheir simplicity and reliablility. The traditional heat pipe is quite difficult tohave a good heat transfer performance through long distance, limiting itsapplication in some extent. The capillary pumped loop (CPL) overcomesthe disadvantage of traditional heat pipe, and can have a good heat transferperformance through long distance with less temperature difference and nopumping energy added. Nanofluid, a new type of working fluid which isbroadly used in heat pipe, has fantastic heat transfer characteristics. Themagnetic nanofluid, also called ferrofluid, will generate extra magneticbody force when imposed with external magnetic field, leading to heattransfer enhancement. The heat transfer enhancement can be useful whenconventional convection heat transfer is inadequate; e.g., in microscaledevices or under reduced gravity conditions. Therefore, ferrofluid has a great potential in the applications of electronics cooling and thermalcontrol systems of spacecrafts.In the present paper, the working principle and operatingcharacteristics of the CPL system, as well as the corresponding CPLdevelopment and application of ferrofluid on heat transfer enhancement atdomestic and abroad are first reviewed. Based on the previousexperimental set-up of a multi-evaporator CPL system, the structures andconfiguration are improved. The number of evaporator is added up to8and a constant temperature water tank is used to provide the cooling water.On the basis of previous work, the starting-up characteristics, the operationperformance and the heat sharing characteristics of the multi-evaporatorCPL system have been systematically investigated in anti-gravitationalconfiguration. The results indicate that the CPL system has a good heatperformance with heat loads ranging from5W to240W, and heat sharingphenomenon is observed. In order to use ferrofluid to enhance the heatperformance of CPL system, a flow and heat transfer model of ferrofluidunder external static non-uniform magnetic field is proposed in order toimprove the application of ferrofluid on heat transfer enhancement. Usingthis model, the two dimensional numerical simulations of ferrofluid flowand heat transfer between two parallel plates are conducted with threecoupled fields, including the flow, the heat and the magnetic fields. Themodel is a fundamental theoretical investigation for the application offerrofluid in CPL systems.